In the prior art, there are different requirements for thermal load of the combustor of a gas water heater or a wall-hanging boiler, according to different demands for the amount and temperature of hot water. For example, when there is a need for a large amount of hot water, the combustor needs to have greater thermal load, while when a small amount of hot water is required, the combustor only needs to have a smaller thermal load.
Currently, thermal load of the combustor is controlled mainly by controlling currents of the proportional valve and the fan. To be specific, when greater thermal load is needed, a larger current will be supplied to the proportional valve, so that the proportional valve can have a bigger opening, and thereby more fuel gas will be allowed to pass through the proportional valve and reach the combustor for combustion; meanwhile, a larger current will also be supplied to the fan to provide the fan with greater rotation speed to increase the flow of combustion air, such that the fuel gas can be better combusted in the combustor, and thereby the combustor has a greater thermal load.
Under ideal conditions, the currents of the proportional valve and the fan are in correspondence relationship with each other, i.e., a determined current allows the proportional valve to have a determined opening. In general, the flow of fuel gas that passes through the proportional valve is in correspondence relationship with the opening of the proportional valve, and, since the flow of the fuel gas is also in correspondence relationship with the flow of combustion-supporting air required for the combustion, the current of the proportional valve and the flow of the combustion-supporting air are also in correspondence relationship with each other. Furthermore, Forming the flow of the combustion-supporting air is in correspondence relationship with both of the rotation speed and current of the demanded fan, so that the current of the proportional valve and the current of the fan are also in correspondence relationship with each other. Due to the above correspondence relationships, the gas water heater and wall-hanging boiler in the prior art mostly apply a method of correspondingly controlling the currents of the proportional valve and the fan, so as to control the thermal load of the combustor.
However, in real life, the operation environments may vary for gas hot water supplying apparatus in different regions, the conventional gas hot water supplying apparatus may well be used in some regions, but in other regions, phenomena of low thermal load or insufficient combustion of the combustor may appear. For example, in different regions the fuel gas pressure may be different, so, when current of the proportional valve is set according to a general standard, it is hard to be adapted to the regions where the fuel gas pressure is lower or higher. For example, in the regions where a fuel gas pressure is lower, there may appear the phenomenon of low combustion load; while in the regions where the fuel gas pressure is higher, there may appear the phenomenon of insufficient combustion of the fuel gas. In addition, in a same workplace, changes may also occur in a pressure of the fuel gas pipeline, which will influence the flow of fuel gas that passes through the proportional valve, and thereby may also lead to the above problems.